I know this is a dumb question, but how do coil spring lifts work?

so like 885 springs with Bilstein 5100. How does the 885 lift the truck higher than the stock spring? Wouldn’t it just compress to the same length?

 

stiffer and/or longer spring. Apply the same load(weight of the truck) and the spring compresses less, therefore ride height is increased

 

Thanks. But isn’t the spring compressed between the shock ring and the top mounting bracket? In other words, you can take the whole spring shock assembly out in one piece. If that is true, how does the load matter?

My non-engineering mind is missing something obvious.

 

Yes, it is captured between the 'top hat' and the lower spring seat and usually has some force applied in doing so. That is referred to as Preload. Preload will directly affect ride height of the truck which is why aftermarket coil over's run threaded spring perches so preload (and therefore ride height/lift) can be adjusted as desired. With a fixed length setup like the factory shock/coil setup, if you run a longer spring now you have to compress that spring farther which therefore requires more pressure preloaded to fit between the upper and lower spring perches. The more preload, the more force is pushed on to the spring and therefore the more weight it takes from that point on to compress it further.
A Spring's strength is measured as pounds/inch, and for our uses is linear rate. You may see a spring listed as a '600lb' or '700lb' spring rate. That means that for every inch the spring collapses it takes another 600 or 700lbs to push the spring down another inch.

So say the front of the truck has 3500lbs on it, each coilover takes half of that as split between left and right.... 1750lbs each assembly. Now if the stock spring is a 12" long and 500lb rate spring it would compress 3.5" (1750lbs/500lbs) to ride height(8.5" now). But if those were replaced with 12" long 700lb springs it would compress 2.5" and therefore the truck would also sit higher up for the same amount of load applied to it as it is now 9.5". It would also take more load to bottom out the stiffer spring.
Another scenario for an aftermarket spring such as an OME 885... if it was still the same 500lb rate spring as stock, but 1 inch longer (13" long unassembled), it will still take 3.5" of compression when the load of the truck is applied since it's the same 500lb rate, however the loaded length would still remain 1" longer since the first 1" was consumed as initial preload to get it to fit it down to the same original assembly length of the coil/shock assembly. It would be 13" length, less 3.5" compression and now be 9.5" long at ride height leading to the truck being lifted, yet still having a softer 500lb rate.

 

Wow thanks for taking the time to explain that and the awesome write up! Makes a lot more sense now.